The extreme energies of UHECR, as high as \(10^{11}\)  GeV, eleven orders of magnitude above the proton mass and "only" eight below the Planck mass, are a unique workbench to probe new ideas, models and theories beyond the Standard Model (SM) of particle physics, which show their effects at energies much larger than those ever obtained, or obtainable in the future, in accelerator experiments. This is the case of theories with Lorentz invariance violations [1]}, [2]}, [3]}, [4]} or models of Super-Heavy Dark Matter (SHDM) [1]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, that connect UHECR observation with the dark sector and cosmological observations.
